The present invention relates to a piston-cylinder type seat belt tensioning device.
In one example of the conventional piston-cylinder type seat belt tensioning devices, a piston connected to a seat belt through a rod is inserted within a cylinder and at an urgent time such as upon an impact of a vehicle, the piston is travelled by pushing force of spring means or the like to pull the seat belt so that a passenger is restrained on his seat.
The seat belt tensioning device of this type comprises a trigger means which usually locks the piston in the cylinder directly or indirectly overcoming the pushing force of the spring means and releases the locking condition only at an urgent time.
One example of such a trigger means as described above has a lock pin for locking the piston in the cylinder, and various kinds of actuator for taking off the lock pin at an urgent time.
However, when the trigger means provided with the lock pin is used, large force is required for releasing the piston from the cylinder so that the actuater becomes complex and large.
Accordingly, one object of the present invention is to provide a seat belt tensioning device provided with a trigger means capable of releasing the locking condition of the piston by small releasing force immediately at an urgent time.